Eyepiece mounting means



Sept 16, 1952 D. E. DAVIDSON EYEPIECE MOUNTING MEANS Filed April 11, 1949 Patented Sept. 16, 1952 UNITED STATES PATENT OFFICE l Claim. 1

This invention relates generally to telescopes, and more particularly, though not inall its aspects, to a telescope having an inclined-axis eye piece.

The telescope of the invention is illustratively of the type commonly employed for spotting in target shooting, observation oi game, birds, and for various all around purposes by sports fans, yachtsmen, airmen, etc., as weil as for certain astronomical and photographic uses. For these miscellaneous purposes it is desirable that the telescope be provided` with interchangeable eye pieces of different powers, that the telescope be convenient to focus. and convenient to look through.

Major objects of the invention are accordingly to provide a telescope for the type of all around service indicated, characterized by con venience of use, particularly convenience and ease of focusing, and an eye piece position of enhanced convenience for the observer; provision for ready interchangeability of eye pieces of different powers; provision of novel and convenient accommodation within the telescope, when not in service, of extra eye pieces of different powers; provision or" a focusing system according to which the eye piece remains xed, focused at all times on a fixed focal plane, While focusing is accomplished by adjustment of the objective; provision of novel and improved means for alining and adjusting the relatively movable cornponents of the objective; and provision of quickly and eiiectively operable means for inserting and locking the eye piece in position in the tele scope.

Additional objects and features of the inven tion by which the various objects are accomplished, will appear in the course of the following detailed description of a presentl illustrative enibodiment thereof, reference being had to the accompanying drawings, in which:

Figure 1 is a plan view of the telescope, with parts broken away to show a section;

Figure 2 is a section taken on broken line 2-2 of Figure 1;

Figure 3 is a section taken on line 3-w3 of Figm ure 1;

Figure 4 is a section taken on line if-#ll oi Figure 2;

Figure 5 is an enlarged detail taken from Fgure 2;

Figure 6 is a detail section. taken on line G-S of Figure 1;

Figure 7 is an elevational detail taken in accordance with line 1 1 of Figure l, but with the eye piece removed;

vFigure 8 is a fragmentary elevational view of the cap and eye piece carrier, one eye piece beu ing shown in transverse section;

Figure 9 is an enlarged detail taken from Figm ure 1; and

Figure 10 is a perspective vier.7 of a preferred prism employed in the telescope.

In the drawings, numeral l designates a gen erally cylindrical casing for the telescope, which is slightly enlarged and internally screwthreaded at its forward end portion, as indicated at li in Figure 1. The internal screwthreads ii extend inwardly for a distance of approximately 2f', terminating at shoulder l2 against which is seat= ed mounting ring I3 for positive objective lens combination i4. Also screwed intothe forward open end of casing i0 is a cap i5 which serves the dual function of closure to protect the ob'a jective when the telescope is not in use, and as a carrier for extra eye pieces, as will be explained in more detail hereinafter. it will of course be understood that this .cap i5 is unscrewed and ren moved, together with the eye pieces which it car ries, when the telescope is in use.

The rearward end of the casing iii is internally screwthreaded, as indicated at 2i), to receive an externally screwthreaded mounting ring 2i, to the rearward side of which is secured, as by screws 22, an annular mounting ring'. .This ring 23 has a wide cylindrical bearing surface 24 on its external periphery, the diameter of which is just sufficiently less than that of casing I0 that a ribbed focusing ring. 25 .rotatably mounted thereon is substantially flush with or just slightly raised above the surface of the cas`1 ing Hl. This focusing` ring 25 is confined bew tween the rearward face of mounting ring 2i and an annular shoulder 26 afforded by external annular iiange 21 formed on the rearward end of mounting ring 23. The focusing ring 25 is thus provided with an annular channel in which it may rotate freely, butwithout,longitudinal or axial movement,

Ring 2l snugly but slidably receives a cylindrin cal tube 38, the forward end of which carries a second and axially movable component 3i oi the telescope objective, this component 3i being in the present instance of negative power, and acting together with positive component id to change the focal length of the combination as it is moved in an axial direction.

The tube 39 is further supported towards the forward end portion thereof Within an adjustment ring 32 which is mounted in casing l0 for lateral adjustment in any direction by a novel mounting means now to be described. As will be observed, the ring 32 fits the interior of casing cylinder I with sufficient clearance to permit the desired lateral adjustment. The rearward exterior corner of the ring 32 is beveled, preferably at 45, as indicated at 33, and this bevel engages a ring 34 snapped into an annular groove 35 formed around the interior of the tube I 0. Three or more screws 36 set into ring 32 from its rearward side have conical heads which en.

gage the ring 34, and it will be evident that as these rings are tightened, the conical heads in coaction with the bevel formations 33 will cam the ring 32 in a direction away from or inward of the casing I0. Clearly, by proper adjustment of the screws 36, the ring 32, and hence the position of the tube 30 and its lens 3|, can be laterally displaced or adjusted with respect to the axis of the objective I4. For ease of action, and to assure against binding, the interior of the ring 32 may be rounded, as indicated at 31, though in ,practice this may not be essential if a very slight clearance or working tolerance is permitted between the ring 32 and the tube 3U. The mounting as thus described enables very convenient alinement of the negative component 3| of the objective with the positive component I4, and is found in practice to reduce very greatly the normal work attendant upon optical alinement of the lens components.

The interior of focusing ring is cut with av helical groove vv4ll, in which engages a follower element 4I secured to the rearward end of a strap 42, the forward end' of which is secured, as by screws 43, to tube at a point near the for-= ward end thereof.

As will be clear from Figures 1, 3 and 6, the mounting ring 2l is formed with an aperture 55 to pass the strap 42,.`while the ring 23 is formed in its periphery with a notch 5I for a similar purpose, the depth of the latter being sufcient to assure that the follower element 4I will be maintained within the helical groove when the parts are in assembly. It will now be evident that the slot 50 and passage 5I function not only to pass and permit longitudinal movement of the strap 42, but also constrain the same against rotation. Accordingly, rotation of focusing ring 25 acts through the coaction of its helical groove 4U with vthe follower element 4I on strap 42 to longitudinally move the strap and lens carrying tube for focusing movement of said lens relative to component I4. i

Ring 23 has a rearward transverse Wall 55 provided with a central light passing aperture 56, and mounted directly against said wall is an erecting prism 51 designed to erect the image, laterally offset it from the axis of the objective and deviate the axis oi' the line of sight through This prism is more fully disclosed in my copending application Serial No. 86,852, filed April ll, 1949, and entitled Telescope and Erecting Prism Therefor; now abandoned.

The forward side of the prism is defined by flat entrance surface B0, disposed at right angles tothe axis of the objective, and the opposite side of the prism is defined by emergent surface 6I, disposed at an angle of 45 with reference to surface 60. The prism is completed by means of two surfaces 62 and 63 at right angles to'one another. A ray R entering the prism along the axis of the objective enters at a (see Figure 10), strikes and is internally reflected in a downward direction by surface 6I at point b, strikes surface 62 and is internally reflected in a lateral direction thereby at point c, strikes surface 63 and is reflected upwardly thereby at point d, thence strikes surface 60 and is internally rei-lected thereby at point e. The last mentioned reflection sends the ray at right angles to emergent surface 6I, the ray emerging at point f. It will be observed that this axial ray has been offset laterally, and deviated through 45 with reference to the axis of the objective, the emergent ray traveling along a 45 line of inclination with reference to the axis of the'objective. The axis of the presently described eye piece 66 is accordingly arranged to be in coincidence with this emergent ray, the eye piece thus extending at an inclination of 45 with reference to the axis of the telescope body, as clearly appears in the drawings. The prism 51 is mounted in proper position directly against the aforementioned wall 63, its upper edge seating against a shoulder 10 of said wall, and its-remote side as viewed in Figure 1 seating against a second shoulder 1I formed on said wall 60. The prism is further held in position by means of a spring 12 which engages it from the rear and is seated in a socket 13 formed inrearward cap 14. Another spring 15 seating on a lug 16 extending from wall 60 engages the prism from one side to hold it against the aforementioned seating shoulder 1 I.

The rearward cap 14 has a countersink 18 which receives the aforementioned flange 21 on the mounting ring 23, being secured to the wall 60 of mounting ringr 23 as by means of screws such as 19. The cap 14, which surrounds and encloses the prism 51, is provided with an inclined uppper wall portion 14a which is generally parallel with the emergent surface 6I of the prism, and this wall 14a is formed with an aperture 80 which snugly receives the eye piece 66. In order to seal against dust and moisture, the aperture 80 is preferably formed with an annular groove 8| which receives an O-ring 82.

The eye piece 66 mounts the usualeye piece lens 84, and includes cylindrical wall 65 having a snug fit within the aperture 80 in wall member 14a. Wall 85 has an external helical thread element 86 of relatively small lead, as indicated best in Figure 5, this thread element being interrupted for an angular extent of aboutv 90".

'I'he underside of this thread element 86 is withl out lead, and is adapted to seat on a machined annular seating surface 90 formed on wall 14a around aperture 8U. 'I'he outer side of thread element 86 has a small helical lead, and is beveled, as at 9|, so as to engage under a correspondingly beveled, arcuate seating surface 92 formed on the under side of a lug 93 formed on the top of cap 14. The lug 93 occupies somewhat less than 90 of angle, so that, when the 90 'gap in the thread elementSG is alined therewith, the eye piece can easily be slipped into the aperture 80, or removed therefrom. Once inside, with the thread element '86 seated on seat 90, an approximately half-turn twist brings the thread element around under the lug 93 until it tightly engages the lug slot v92. Because of the wedging engagement of the bevels on the thread element 8B and seat 92, the parts bind together very tightly with but little finger effort, andthe eye piece is very tightly locked in position. This may be best understood from an inspection of Figure 5, from which it may be seen that the wedging action spoken of will force the underside of the thread element 86 tightly down against seat 90 and will at the same time force the body 85 of the eye piece tightly against the surface a of aperture 80 on the side opposite from the lug 93. l

The optical design is such that the objective forms its image in a fixed focal plane between the rearward prism face 6| and the eye piece lens. With the eye piece removed, a camera can if desired be focused on this focal plane and a photograph be so made.

Returning now to a consideration of the removable eye piece carrying cap I5 Which closes the forward end of the telescope when not in service, this cap has a screwthreaded wall which screws into the tube l0 until its shoulder I0| engages the end of said tube, as indicated in Figure l. The end wall |02 of the cap is formed inside this wall |00 with three circular sockets |03 adapted to snugly receive the cylindrical body parts 85 of three eye pieces 66. The peripheries of these three sockets are tangent to the inner surface I of wall |00, and sunk into the wall surface 105 is an annular locking groove |06 adapted to receive the thread elements 86 on the eye pieces. Like on the lug 93, the outer side of this groove is preferably beveled, as at 101, so as to afford a wedging action as the beveled helical thread element 86 engages thereagainst. The gap in the thread element, when turned to face the wall surface 105, permits the eye pieces to be inserted until the thread-element engages the end wall |02, after which a simple twist moves the thread element into the groove until a binding engagement is achieved. The casing I0 is of sufficient length forwardly of the objective I4 that the spare eye pieces carried by the cap l5 cannot interfere with the objective. This same extension of the casing forward of the objective serves as a desirable sun shade.

Attention is particularly directed to the convenient focusing arrangement provided by the invention. Focusing is accomplished by a convenient operation of the ring 25, rather than by adjustment of the eye piece, and this focusing ring 25 is separated from the eye piece by a substantial distance, so that the eye piece will not be interfered with, or its lens perhaps smudged, in the operation of focusing.

It will of course be understood that the drawings and description are for` illustrative purposes only, and that various changes in design, structure and arrangement may be made without departing from the spirit and scope of the appended claim.

I claim:

Mounting means for an eye-piece in a body part of an optical instrument, said eye-piece having a cylindrical portion at the forward end thereof, and said body part of said instrument having a xed wall part formed with a cylindrical aperture in which said cylindrical forward end body part of said eye-piece is slidingly receivable, an external thread element extending part way around said cylindrical portion of said eye-piece, said thread element having a forward side surface Without lead and a rearward side surface having a helical contour, an annular seat on said fixed wall part around said cylindrical aperture engageable by the leadless forward side surface of said thread element, and a single ledge on said fixed wall part, on one side only of said aperture in said Wall part, projecting into overhanging relation with respect to a portion of said annular seat and spaced from said seat, said ledge having an arcuate seat opposite said portion of said annular seat engageable by said rearward helical side surface on said thread element when said eye-piece is twisted in said aperture with said forward side surface of said thread in engagement with said annular seat, said rearward helical surface of said thread element, and said arcuate seat on said overhanging ledge, being bevelled at obtuse angles with respect to the extent of the cylindrical portion of the eye-piece that is rearward of said thread element, said heiically contoured thread element causing said thread element to be forced against said annular seat on said body part, and said bevelled surfaces on said thread elenient and ledge coacting to force said thread element and the cylindrical portion of the eye-piece in a lateral direction to cause binding engagement between said cylindrical portion and the interior surface of said cylindrical aperture on the side opposite from said ledge, when said eye-piece is twisted to bring said helical, bevelled surface of said thread element into forcible engagement with said bevelled arcuate seat on said ledge.

DONALD E. DAVIDSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 287,904 Bulloch Nov. 6, 1883 1,796,456 Halldorson Mar. 17, 1931 2,184,351 Langsner Dec. 26, 1939 2,245,405 Langsner June 10, 1941 2,291,821 McNabb Aug. 4, 1942 2,351,747 Eckert June 20, 1944 2,362,603 Wittel Nov. 14, 1944 

